This paper presents the heat transfer coefficients and the pressure drop measured during HFO1234yf condensation inside a brazed plate heat exchanger: the effects of saturation temperature, refrigerant mass flux and vapour superheating are investigated. The heat transfer coefficients show weak sensitivity to saturation temperature and great sensitivity to refrigerant mass flux. At low refrigerant mass flux (u3c 20 kg/m2s) the heat transfer coefficients are not dependent on mass flux and condensation is controlled by gravity. For higher refrigerant mass flux (u3e 20 kg/m2s) the heat transfer coefficients depend on mass flux and forced convection condensation occurs. The condensation heat transfer coefficients of super-heated vapour are from 8 to 11% higher than those of saturated vapour. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow and therefore a quadratic dependence on the refrigerant mass flux. HFO1234yf exhibits heat transfer coefficients lower (10-12%) and frictional pressure drop lower (10-20%) than those of HFC134a under the same operating conditions.
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机译：本文介绍了在钎焊板式换热器内HFO1234yf冷凝过程中测得的传热系数和压降：研究了饱和温度，制冷剂质量通量和蒸汽过热的影响。传热系数对饱和温度的灵敏度较弱，对制冷剂质量通量的灵敏度较高。在较低的制冷剂质量通量（20 kg / m2s）下，传热系数与质量通量无关，冷凝作用由重力控制。对于更高的制冷剂质量通量（20 kg / m2s），传热系数取决于质量通量，并且会发生强制对流冷凝。过热蒸气的冷凝传热系数比饱和蒸气的冷凝传热系数高8至11％。摩擦压降与制冷剂流量的每单位体积的动能呈线性关系，因此与制冷剂质量通量呈二次关系。在相同的工作条件下，HFO1234yf的传热系数比HFC134a的传热系数低（10-12％），而摩擦压降则低（10-20％）。
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